How do I know *when* to use Conditional Premises? Is it only after I've exhausted all other methods? Also, could you explain to me briefly why one is allowed to say that a statement true, if its truth is based on something that you simply defined earlier? It just doesn't make sense to me at this point.

How do I know *when* to use Conditional Premises? Is it only after I've exhausted all other methods? Also, could you explain to me briefly why one is allowed to say that a statement true, if its truth is based on something that you simply defined earlier? It just doesn't make sense to me at this point.

The statement “If S then R” means if S is true then R must be true.
Another way to put that is: “R follows from the truth of S”
So if the conclusion of an argument is a hypothetical then by assuming the premise the hypothetical is true and demonstrating that the conclusion of the hypothetical must follow then we have shown that hypothetical is true.